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Exercising in Space

Why is Exercise Important in Space?

Exercising in space is not just for fun; it is necessary to keep astronauts healthy and functional. On Earth, gravity works against our muscles and bones every time we move. This requires our bodies to maintain enough muscle and bone mass to support our own weight. In the weightless environment of space, where the relative force of gravity is minute, astronauts lose muscle mass and bone density since it is not required to support their weight.

Exercising in space is the most effective way to date to compensate for the relative lack of gravity. However, even with rigorous exercise, astronauts have typically lost up to 0.4-1% of their bone density per month in space. Although astronauts gradually recover their muscle tissue and most of their bone mass when they return to Earth, it is important that they are strong enough to perform strenuous activities in space, such as spacewalks, and emergency procedures during landing. Completing a regular exercise routine in space prepares the astronaut for these situations and also facilitates a shorter period of reconditioning to recover their muscle and bone.

A recent study has shown that the International Space Station (ISS) astronauts who use the Advanced Resistive Exercise Device (ARED) daily, eat sufficient calories and have adequate vitamin D during a four to six month mission are able to maintain bone in most regions of their body. In addition, although astronauts return to Earth with the same body weight, they have a lower percentage of fat mass and a higher percentage of muscle mass. Researchers are now investigating if the strength of astronauts' bones post-flight is as good as before their flight.

How Often do Astronauts Exercise in Space?

Astronauts who live on the ISS for periods up to 6 months are required to exercise for approximately two hours per day. Each astronaut's exercise routine is monitored, and can be adjusted if necessary based on his or her monthly fitness assessment and data from daily exercise sessions. If astronauts are scheduled to perform a spacewalk, their exercise routines may be altered or restricted.

Exercise Equipment

ISS crewmembers use a cycle ergometer for cardiovascular exercise, a treadmill for cardiovascular exercise, loading the skeletal system and maintaining the neuromuscular patterns for locomotion, and a Resistance Exercise Device for maintaining muscles and bones.

The cycle ergometer is similar to a stationary bicycle. The astronaut uses clip pedals and has the option of a back support and hand holds to secure him/her to the machine.

The treadmill uses a bungee and harness system to secure the astronaut to the treadmill. The bungees attached to either side of the treadmill and to the harness and apply a load, based on the astronaut's body weight, to the shoulders and hips. At the start of an ISS mission, the loading is set at 60% of an astronaut's body weight. The astronaut increases the loading throughout the mission with a goal of attaining 85%-100% body weight of loading. Increasing the loading makes the workout more challenging.

The ARED employs vacuum cylinders to apply a load of up to 600 lb to a bar or a cable so that astronauts can perform heel lifts, squats, deadlifts, and other exercises, to strengthen the muscles that do not get much use in space. This device mimics weightlifting on Earth.

The exercise equipment operates with vibration isolation systems to prevent the forces created by the astronauts working out on the equipment from disturbing scientific experiments.

Cosmonaut Gennady I. Padalka, Expedition 9 commander representing Russia's Federal Space Agency, exercises on the Cycle Ergometer with Vibration Isolation System in the Destiny laboratory of the International Space Station (ISS). May 20, 2004. (Credit: NASA)

Canadian Space Agency (CSA) Astronaut Bob Thirsk, Expedition 20/21 flight engineer, exercises on the Treadmill Vibration Isolation System in the Zvezda Service Module on the International Space Station (ISS). Note the subject-loading device around his shoulders and chest securing him to the treadmill. November 11, 2009. (Credit: NASA)

Canadian Space Agency (CSA) astronaut Chris Hadfield works out with the Advanced Resistive Exercise Device (ARED) located in the Unity module of the International Space Station (ISS). January 11, 2013 (Credit: NASA)